For many years now, the trucking industry has served this nation by transporting goods throughout the country. The trucking industry has grown in importance and sophistication. Trucks towing tailers laden with goods are seen everywhere on the highways, and the goods transported provide the very lifeblood of many communities which have no access to other forms of freight transportation.
As the trucking industry has grown, it has become increasingly more important to provide safety features for the trucks and trailers. The truck and trailer operators share the highways with the public, and thus, they also share the responsibility to make travel on the highways as safe as possible.
Of course, one of the primary areas for safety concerns is the means by which a trailer is coupled to a truck or another trailer. These coupling means must be able to withstand pulling, jolting, and twisting forces in almost every conceivable direction because a truck and trailer rig in use is constantly encountering bumps, turns, speed changes, etc. which cause such inevitable, but unpredictable forces. Inferior hitch devices have caused some serious accidents when they have failed to retain a trailer in tow. It is difficult to imagine something more frightening than encountering a runaway, fully-loaded truck trailer which is rolling down the highway without brakes or steering. But, this is exactly what happens when the hitch device fails and accidentally releases the trailer.
Because of such safety concerns and various practical problems, many different types of hitch devices have been developed over the years. There have been tongue and pin, hook and eye, ball and socket, and pintle hook hitch devices, among others. Each type of hitch device has its advantages and its disadvantages.
The tongue and pin hitch device is a simple device having a few component parts and is frequently used to connect farm equipment. It is easy to engage by aligning a hole in a trailer or wagon tongue over a hole in a corresponding tongue on the tractor or truck and by dropping a pin or bolt therethrough. The pin prevents the tongues from pulling apart. However, in use, the pin sometimes breaks under the strain of extreme forces exerted directly on the pin or the pin bounces or works its way upward out of the tongue holes. In either case, the pin fails and releases the tongues from each other. To prevent displacement of the pin, a nut may be threaded onto the pin or bolt or a cotter pin may be threaded through a bore in the pin to inhibit upward displacement of the pin. Such precautions have not been entirely successful.
The hook and eye hitch device is another rather simple device which is easy to use. One simply places a draw bar with an eye fixed to one vehicle over a hook fixed to the other vehicle and a connection is complete. Again, however, when the hook and eye hitch device is jostled about during use, it is not uncommon for the eye to work its way free from the hook and cause disengagement of the trailer.
The ball and socket hitch device is commonly used with smaller trailers such as travel trailers, horse trailers, small self-haul moving trailers, and the like. The ball and socket hitch works on a principle that the socket connected to a trailer tongue clamps down on a ball such that vertical movement of the socket is inhibited but swinging or rotating movement in a substantially horizontal direction is not. This enables the trailer to take turns and to absorb some of the shocks incident to towing a trailer. To assure that the socket remains clamped to the ball, many different types of locking mechanisms have been used, most of which cause a lip or flange to encircle the underside of the ball. The lip or flange is designed to grasp the ball if the socket is forced to move vertically, thereby preventing disengagement. Despite the various types of locking mechanisms used to secure ball and socket hitch devices, it is not uncommon for the locking mechanism to fail and have the trailer free itself during use.
Due to the failings and limitations of the above-mentioned hitch devices, such devices are usually not suitable for use in the trucking industry. A heavy duty, dependable hitch device must be used. To accomplish the needs of the trucking industry, the pintle hook hitch device has been designed and improved over the years. The pintle hook hitch is similar to the hook and eye hitch discussed above, but it is more sturdy and it has a retainer arm which opens and closes the mouth of the hook portion called the pintle. The retainer arm is usually movable in a vertical direction on a pivot pin or shaft and movement is activated by a lever or handle. Thus, when the retainer arm is in its vertical or upright position the hook is open to receive a coupling eye. Then, the retainer arm can be swung to its closed position whereby the coupling eye is secured within the grasp of the hook and vertical movement of the coupling eye is limited.
To assure that the retainer arm remains in its closed position while a trailer is being towed, a number of locking mechanisms have been used. Some of the locking mechanisms are internal of the pintle hook such as that illustrated in U.S. Pat. No. 2,842,380 entitled "Double Lock Trailer Coupling" issued to D. S. Weiss on July 8, 1958, and some employ external apparatus such as that illustrated in U.S. Pat. No. 3,475,037 also entitled "Double Lock Trailer Coupling" issued to D. S. Weiss on Oct. 28, 1969.
With respect to internal locking mechanisms, some significant drawbacks have been encountered. Internal locking mechanisms are not easily accessible for repair in the event of a malfunction. Also, such mechanisms are not visible to the eye; thus, a user can never be absolutely certain that the mechanism is fully engaged. On occasion, retainer arms have not actually been locked into position even though they appeared to be secure from outward appearances. Most significantly, internal locking mechanisms must be installed during fabrication of the pintle hook device and cannot be added as a safety accessory at a later time. Further, under the tremendous forces, jolting and jarring that occur during use, such internal locking mechanisms have been known to break or fail for one reason or another. In some of those cases, the retaining arm is released, or is sheared off, disengaging the coupling and creating the extremely dangerous runaway trailer situation.
The external locking mechanisms have also presented some drawbacks. Typically, such mechanisms require secondary retaining arms which hold the retaining arm in position. Thus, the exterior design of the pintle hook device is altered such that the secondary retaining arm must be installed during fabrication of the pintle hook device. Consequently, such external locking mechanisms cannot be added to an existing pintle hook device. Additionally, safe operation of external locking mechanisms to avoid pinching of fingers, etc. frequently requires more than one person. Further, such locking mechanisms do not solve the problem where the retainer arm is sheared off due to forces encountered during use.
It is an object of the present invention to provide an improved safety mechanism for hitch devices, and in particular, hitch devices of the pintle hook type.
Another object of the present invention is to provide a safety mechanism which is external of the pintle hook device that can be installed as an accessory of an existing pintle hook device.
A further object of the present invention is to provide a safety mechanism which is easy to operate by one person.
Still another object of the present invention is to provide a safety mechanism which compensates for and is able to withstand the forces, jolting and jarring encountered during use in towing a trailer.
A further object of the present invention is to provide a safety mechanism which will reduce the likelihood of the coupling becoming disengaged either through unintended release or through the shearing off of the retaining arm.
Another object of the present invention is to provide a safety mechanism that will automatically--without the operator's intervention or action--fall into a safety locking position when the pintle hook device is closed.
A further object of the present invention is to provide a safety mechanism which the operator can easily and readily see is in a safety locking position.
An additional object of the present invention is to provide a safety mechanism which can be used in conjunction with other safety locking mechanisms to impart additional security into use of the hitch device.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawings.